Process for heating glass sheets therewithin a forced convection heating apparatus by controlling impingement velocity

ABSTRACT

A forced convection heating apparatus and process for heating glass sheets therewithin. The apparatus includes at least one gas burner for producing hot combustion gases which is to be distributed toward and into contact with the top and/or bottom surfaces of a glass sheet within the apparatus housing. The velocity of the distributed hot combustion gases which eventually impinges upon the top surface of the glass sheet is controllable independently of the impingement velocity of the hot combustion gases being distributed, and, in turn, directed toward and into contact with the bottom surface of the glass sheet.

This application is a division of application Ser. No. 08/263,649, filed Jun. 20, 1994 now U.S. Pat. No. 5,672,191.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to apparatuses and processes associated with the heating of glass sheets, and, more particularly, to a forced convection heating apparatus and process for heating glass sheets therewithin.

2. Statement of the Prior Art

Heating-of glass sheets within a furnace, and, more particularly, in a gas-fired forced convection furnace, has been known in the art for several years. Indeed, one such type of prior art gas-fired furnace conveys a sheet of glass through the furnace on a bed of air. As the glass "floats" through the furnace, hot air is distributed toward and into contact with the top and bottom surfaces of the glass sheet. However, due to the complexity of a "floating" system, prior art devices of this type typically use convective heat flow to the bottom surface of the glass sheet, and radiant heat flow to the top surface of the glass sheet.

After the convective heat has impinged the bottom surface of the glass sheet, a portion of the "spent" heat/fluid is randomly returned toward a proximally positioned gas burner where the spent fluid and newly produced convective heat/fluid are mixed and then recirculated toward impingement of same on the glass sheet.

Furthermore, prior art gas-fired heating devices have also been used in which convective heat that is to impinge upon the top surface of a glass sheet is distributed from one or more gas burners located above the glass sheet as it passes through the device, and, convective heat that impinges the bottom surface of the glass sheet is distributed by one or more gas burners located below the glass sheet.

Although such prior art devices have indeed disclosed recirculation of spent hot combustion fluid and use of gas-fired burners, none of such prior art devices disclose, much less suggests, drawing spent hot combustion fluid toward and into a mixing chamber operably and closely positioned about a substantial portion of a gas burner--in which the gas burner is specifically intended to produce, for distribution, hot combustion gases to the respective top and/or bottom surfaces of the glass sheet being heated.

In addition, none of such prior art devices disclose, much less suggests, the use of gas-fired burners operably positioned above and below the glass sheet for producing and, in turn, distributing, forced convective flow of the hot fluid to corresponding ones of the top and bottom surfaces of the glass sheet in which: (1) the temperature of the hot combustion gases from each of the gas burners can be controlled independently of each other; and/or (2) the impingement velocity of the hot combustion gases being distributed onto the top and bottom surfaces of the glass sheet can be independently controlled--toward uniform control of convection heat transfer to the top and bottom surfaces of the glass sheet, to, in turn, compensate for glass thickness, coating and color, among other variables.

These and other features of the present invention will become apparent in light of the present Specification, Claims and Drawings.

SUMMARY OF THE INVENTION

The present invention comprises a forced convection heating apparatus for heating glass sheets, in which the glass sheets each have a top surface and a bottom surface. The apparatus includes a housing having an interior region and means for conveying a glass sheet through the interior region. Gas burner means are operably associated with the housing for producing hot combustion fluid.

The apparatus further comprises first means for distributing, and in turn, impinging, at least part of the hot combustion gases from the gas burner means to the bottom surface of the glass sheet within the interior region of the housing, for distributing, and, in turn impinging at least part of the hot combustion gases from the gas burner means to the top surface of the glass sheet.

First impingement velocity control means control the impingement velocity of the hot combustion gases into contact with the bottom surface of the glass sheet within the interior region of the housing, and second impingement velocity control means control the impingement velocity of the hot combustion gases into contact with the top surface of the glass sheet. The first and second impingement velocity control means are each operable, and in ram, controllable independently of each other.

In the preferred embodiment of the invention, the gas burner means produces the hot combustion gases at a predetermined temperature. In such an embodiment, the apparatus further comprises first means for adjusting the temperature of the hot combustion gases prior to impingement of same on the bottom surface of the glass sheet within the interior region of the housing. In addition, second means are also included for adjusting the temperature of the mixed hot combustion gases prior to impingement of same on the top surface of the glass sheet. The first and second temperature adjustment means are operable, and, in turn, adjustable, independently of each other.

In another preferred embodiment of the invention, the forced convection heating apparatus further comprises a mixing chamber operably positioned about at least a portion of the gas burner means. The mixing chamber has a proximal end operably associated with the first and second distributing means, and a second open end distally spaced from the proximal end.

In this preferred embodiment, the invention further includes means for directing spent hot working fluid, which has impinged upon at least one of the top and bottom surfaces of the glass sheet, toward and into the mixing chamber for operable mixing of at least part of the spent hot working fluid with newly produced hot combustion gases from the gas burner means toward transfer of same into at least one of the first and second distributing means and, in turn, toward and into operable contact with at least one of the top and bottom surfaces of the glass sheet within the interior region of the housing.

The forced convection heating apparatus further comprises means for causing a mixture of the spent hot working fluid, which has impinged, and, in turn, bounced off at least one of the top and bottom surfaces of the glass sheet, and the newly produced hot combustion gases within the mixing chamber. The mixture means comprises a plurality of apertures integrally formed in the gas burner means for release of the hot combustion gases in a direction substantially perpendicular to the longitudinal axis of the gas burner means. The spent hot working fluid is operably sucked into the mixing chamber in a direction substantially perpendicular to the newly produced hot combustion gases as it is being operably released from the gas burner means to, in ram, result in a mixture of the spent working fluid and newly produced hot combustion gases.

In the preferred embodiment of the invention, the directing means includes at least one fan operably associated with the mixing chamber for sucking at least part of the spent hot working fluid that has impinged upon at least one of the top and bottom surfaces of the glass sheet within the interior region of the housing toward and into the mixing chamber.

Also in this preferred embodiment, the first and second distributing means each includes at least one fan and at least one combustion air conduit member operably associated with a corresponding fan. Each of the combustion air conduit members has at least one nozzle member operably positioned adjacent a corresponding one of the top and bottom surfaces of the glass sheet within the interior region of the housing for operably dispensing, and, in ram, impinging at least part of the hot combustion gases toward and onto the adjacent top and bottom surfaces of the glass sheet.

The first and second distributing means further include a plenum member operably positioned between corresponding ones of the fans and combustion air conduit members. The preferred embodiment of the invention includes a process for heating a sheet of glass in a force convection heating furnace, in which the furnace includes; a housing having an interior region and the glass sheet has a top and bottom surface.

The process comprises the steps of: (a) inserting a glass sheet into the interior region of the housing; (b) producing hot combustion gases from at least one gas burner; (c) distributing the hot combustion gases from the at least one gas burner toward and into operable contact with at least a portion of the top and bottom surfaces of the glass sheet within the interior region of the housing; (d) controlling impingement velocity of the hot combustion gases being distributed toward and onto the bottom surface of the glass sheet within the interior region of the housing; (e) controlling impingement velocity of the hot combustion gases being distributed toward and onto the top surface of the glass sheet--in which the controlling of the impingement velocity of the hot combustion gases being distributed toward and onto the top and bottom surfaces, respectively, of the glass sheet, is controllable independently of each other.

In the preferred embodiment, the process for heating a glass sheet within a forced convection furnace further comprises the steps of: (a) sucking at least a portion of spent hot working fluid, which has operably contacted at least one of the top and bottom surfaces of the glass sheet, toward and into a mixing chamber operably associated with a corresponding gas burner--in which each of the mixing chambers are operably positioned about a least part of a corresponding gas burner; (b) mixing the spent hot working fluid in the mixing chamber with the hot combustion gases as it is being produced from a corresponding gas burner; and (c) distributing the mixed spent hot working fluid and the newly produced hot combustion gases toward and into operable contact with at least one of the top and bottom surfaces of the glass sheet within the interior region of the housing.

In another preferred embodiment of the invention, the process for heating a sheet of glass in a forced convection heating furnace further comprises the steps of: (a) adjusting the temperature of the mixed spent hot working fluid and newly produced hot combustion gases prior to impingement of same onto the bottom surface of the glass sheet; and (b) adjusting the temperature of the mixed spent hot working fluid and newly produced hot combustion gases prior to impingement of same onto the top surface of the glass sheet. The adjusting of the temperature of the mixed fluids that are to impinge the top and bottom surfaces, respectively, of the glass sheet, being adjustable independently of each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the drawings is a perspective view of the forced convection heating apparatus in partial Cross-section and in partial break-away;

FIG. 2 of the drawings is a side cut-away view of the forced convection heating apparatus;

FIG. 3 of the drawings is a cross-sectional view of the forced convection heating apparatus taken generally along lines 3--3 of FIG. 2;

FIG. 4 of the drawings is a cross-sectional view of the forced convection heating apparatus taken generally along lines 4--4 of FIG. 3; and

FIG. 5 of the drawings is a cross-sectional view of an array of the first and second distributing means, showing, in particular, distribution of hot combustion gases out of the corresponding nozzles, and, accordingly toward and into contact with the top and bottom surfaces of a glass sheet within the interior region of the housing of the forced convection heating apparatus.

FIG. 6 of the drawings is a perspective view of the nozzles.

DETAILED DESCRIPTION OF THE DRAWINGS

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail, one specific embodiment with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.

At the outset, although it is contemplated that forced convection heating apparatus 10 (FIG. 1) be constructed with multiple gas burners, related distribution and recirculating assemblies/units, only two of such assemblies/units will be explained in detail--since any additional units would comprise substantially the same components and intercooperation therebetween.

Forced convection heating apparatus 10 is shown in FIG. 1 and FIG. 3 as comprising housing 12, conveying means 14, first gas burner means 16, second gas burner means 18; first distributing means 20, second distributing means 22, first mixing chamber 26, second mixing chamber 28, first directing means 30, second directing means 32 (FIG. 3), first temperature adjusting means 33 (FIG. 1), second temperature adjusting means 34 (FIG. 1), swirling mixture means 36 (FIG. 3) and first and second impingement velocity control means.

Housing 12, as shown in FIGS. 1-3, includes upper section 40, lower section 41, and interior region 42. Conveying means 14, which may comprise a plurality of ceramic rollers, are operably positioned between the upper and lower sections of housing 12, and are used to convey a glass sheet, such as glass sheet 100 (FIG. 2 and FIG. 3) through interior region 42 of housing 12. Glass sheet 100 includes top surface 101 and bottom surface 102. As can be seen in FIG. 2 and FIG. 3, when glass sheet 100 is operably positioned within interior region 42 of housing 12, top surface 101 will be operably exposed to upper section 40 of housing and bottom surface 102 will be operably exposed adjacent lower section 41 of housing 12.

First distributing means 20 is shown in FIG. 3 as comprising fan 45, working fluid conduit 46, and plenum member 47. Working fluid conduit 46 includes a plurality of male insert members, such as male insert member 48, 48' (FIG. 3) which are operably seated within corresponding receptacles, such as receptacles 80, 80' (FIG. 4) of the corresponding plenum member 47 (FIG. 4), and a plurality of nozzles, or jets, 50 (FIG. 5). As will be explained in greater detail, nozzles 50 comprise a plurality of apertures, such as apertures 70-72 (FIG. 5), for operable release of hot combustion gases, in a spray-like manner, toward and into contact with bottom surface 102 of glass sheet 100.

Second distributing means 22 is also shown in FIG. 3 as including fan 52, working fluid conduit 53, and plenum member 54. Working fluid conduit 53 of the second distributing means also includes a plurality of male insert members 49, 49' (FIG. 3) for operable insertion into corresponding receptacles (not shown) of plenum member 54, and nozzles 56 (FIG. 5). These nozzles, like nozzles 50 of first distributing means 20, enable hot combustion gases produced from a corresponding gas burner means 18 (FIG. 3) to be released toward and into operable contact with top surface 101 of glass sheet 100.

First mixing chamber 26 and second mixing chamber 28 are shown in FIG. 3 and FIG. 4. As can be seen, first mixing chamber 26 is operably positioned about part of first gas burner means 16, and second mixing chamber 28 is operably positioned about part of second gas burner means 18. Both the first and second mixing chambers 26 and 28, respectively, include a proximal end 65 and 67, respectively, and an open end 68 and 69, respectively--in which the proximal ends are operably positioned adjacent a corresponding fan, such as fans 45 and 52 (FIG. 3).

The fans, such as fans 45 and 52, which, among other things, serve to distribute hot combustion gases from the respective gas burner means toward and into eventual contact with the glass sheet, also serve as part of the directing means for sucking spent hot working fluid that has impinged on the top and bottom surfaces 101 and 102, respectively, of glass sheet 100, toward and into a corresponding one of the first and second mixing chambers 26 and 28, respectively (as shown by the direction of the arrows in FIG. 3). Although first and second directing means 30 and 32, respectively, each use fans 45 and 52, respectively, for sucking spent hot working fluid into a corresponding mixing chamber.

As the spent hot working fluid is drawn into the respective mixing chambers, a mixing will occur between the spent working fluid and the newly produced hot combustion gases because of mixture means 36 (FIG. 3). As can be seen in FIG. 3, the mixture means comprises a plurality of apertures, such as apertures 90-95, integrally formed through each of the gas burner means, such as gas burner means 16 and 18, coupled with the substantially parallel flow of the spent hot working fluid, relative to the longitudinal axis of the respective gas burner means, as it enters the mixing chamber. Accordingly, since the newly produced hot combustion gases are being released through apertures, such as apertures 90-95, in a direction substantially perpendicular to the longitudinal axis of the gas burner means, the spent hot working fluid being sucked into the mixing chamber will, in effect, collide with the newly released hot combustion gases, to, in turn, result in a mixture of spent working fluid and newly produced hot combustion gases.

First and second temperature adjusting means 33 and 34, respectively, are shown in FIG. 1 as comprising thermocouples--although any other type of conventional mechanism for altering the temperature of the hot combustion gases to be produced, or after it is produced, from a corresponding one of the gas burner means, is also contemplated for use. As will be explained, each of the temperature adjusting means independently controls the temperature of the hot combustion gases being produced from a dedicated one of the gas burner means.

First and second impingement velocity control means are shown in FIG. 3, in which impingement velocity of the hot working fluid being distributed toward and into the top and bottom surfaces of the glass sheet is independently controlled by adjusting the speed of the shaft of fans, such as shafts of fans 45 and 52. Such controls enable the impingement velocity of the hot working fluid being directed toward and into contact with the top surface of the glass sheet to be adjusted independently, and, in ram, at a different velocity than the hot working fluid being directed toward and into the bottom surface of the glass sheet--if so desired.

In operation, glass sheet 100 is inserted within interior region 42 of housing 12 through a glass sheet insertion inlet (not shown), and, transfer of the glass sheet through the interior region of the housing is accomplished by conveying means 14. Although the conveying means may comprise ceramic rollers, other types of rollers or other conventional conveying mechanisms are also contemplated for use.

As glass sheet 100 is being conveyed through housing 12, top surface 101 will be operably exposed adjacent a portion of second distributing means 22, and more particularly, adjacent the nozzles in combustion air conduit 53 (as shown in FIG. 5). Accordingly, bottom surface 102 of glass sheet 100 will be operably positioned adjacent a portion of first distributing means 20, and more particularly, adjacent to the nozzles 50 of combustion air conduit 46. Nozzle 50 is comprised of two parallel plates spaced apart by separators 71 and held together by fasteners 72. It is conceivable that different other types of embodiments of this structure are possible including nozzles that distribute the hot combustion gases in a radial arc. As can be seen in FIG. 2 and FIG. 5, the nozzles 50 of combustion air conduit 46, of first distributing means 20, are operably positioned between the individual rollers of conveying means 14. Such an orientation facilitates relatively unobstructed impingement of the hot combustion fluid toward and onto bottom surface 102 of glass sheet 100.

In addition, as glass sheet 100 is being conveyed through housing 12, each of the gas burner means, such as gas burner means 16 and 18, respectively, will be producing hot combustion gases at a desired temperature. Inasmuch as the sheet of glass to be heated may be of a type different than that of a sheet of glass previously heated in apparatus 10 (e.g. different glass colors, surface treatments and/or thicknesses, among other variables), it is important to note that the temperature of the hot working fluid being produced from each of the respective gas burner means, as well as the impingement velocity of same, can be controlled independently of each other (by corresponding temperature adjusting means and impingement velocity control means) to, in turn, enable independent control of convection heat transfer to the top and bottom surfaces 101 and 102, respectively, of the specific glass sheet 100 being heated. Indeed, such independent controlling of temperature and/or velocity enables different types of glass sheets to be processed at a substantially constant rate within apparatus 10--without the necessity of altering the speed at which the glass is conveyed through the apparatus.

As the hot combustion gases are being produced from the gas burner means, it will be released from the apertures therein, and thin will flow in the direction of the arrows, as shown in FIG. 3. As previously explained, such a flow pattern will occur as a result of corresponding fans 45 and 52, respectively, drawing the hot working fluid toward and into respective ones of working fluid conduits 46 and 53 of first and second distributing means 20 and 22, respectively. The hot combustion gases will then continue to travel through the respective combustion air conduits until it is released through corresponding nozzles, such as nozzles 50 and 56, where the hot working fluid will then impinge upon the adjacently positioned top and bottom surfaces 101 and 102, respectively, of glass sheet 100--toward operable heating of same.

After the newly produced hot working fluid has impinged the glass sheet, the fluid that has impinged top surface 101 of glass sheet 100 will, in effect, bounce there off, and this spent hot working fluid will then be drawn into second mixing chamber 28. Similarly, the newly produced hot combustion gases that have impinged bottom surface 102 of glass sheet 100, will also bounce there off and, in turn, be drawn into first mixing chamber 26--as shown by the direction of the arrows in FIG. 3 and FIG. 5.

As previously explained, the spent hot working fluid is drawn into the respective mixing chambers became of suction caused by the corresponding fans, such as fan 45, and the relatively hot temperature of the newly produced hot combustion gases from the associated gas burner means, such as gas burner means 16. As also previously explained, the spent hot working fluid and the newly produced hot combustion gases mix together within the respective mixing chambers in a swirling fashion, to, in turn, result in a substantially uniform mixture of the fluids for further, recirculated, distribution of the mixed fluids to the respective top and bottom surfaces of the glass sheet.

The description and drawings merely explain and illustrate the invention and the invention is not limited thereto except since the appended Claims are so limited as those skilled in the art who have the disclosure before they can make modifications and variations therein without departing from the scope of the invention. 

What is claimed is:
 1. A process for heating a sheet of glass in a forced convection heating apparatus, wherein the apparatus includes a housing having an interior region and the glass sheet has a top and bottom surface, the process comprising the steps of:inserting a glass sheet into the interior region of the housing; producing hot combustion gases from at least one gas burner; distributing the hot combustion gases from at least one gas burner toward and into operable contact with at least a portion of the top and bottom surfaces of the glass sheet within the interior region of the housing; controlling impingement velocity of the hot combustion gases being distributed toward and onto the bottom surface of the glass sheet within the interior region of the housing; and controlling impingement velocity of the hot combustion gases being distributed toward and onto the top surface of the glass sheet within the interior region of the housing, the controlling of the impingement velocity of the hot combustion gases which are being distributed toward and onto the top and bottom surfaces, respectively, of the glass sheet, being controllable independently of each other.
 2. The process according to claim 1 wherein the process for heating a glass sheet within a forced convection apparatus further comprises the steps of:sucking at least a portion of spent hot working fluid, which has operably contacted at least one of the top and bottom surfaces of the glass sheet, toward and into a mixing chamber operably associated with a corresponding one of the at least one gas burner; each of the mixing chambers being operably positioned about at least a portion of a corresponding one of the at least one gas burner; mixing the spent hot working fluid in the mixing chamber with the hot combustion gases being produced from a corresponding one of the at least one gas burner; and distributing the mixed spent hot working fluid and the newly produced hot combustion gases toward and into operable contact with the at least one of the top and bottom surfaces of the glass sheet within the interior region of the housing.
 3. The process according to claim 2 wherein the process for heating a sheet of glass in a forced convection heating apparatus further comprises the steps of:adjusting the temperature of the mixed spent hot working fluid and newly produced hot combustion gases from the mixing chamber which is to come into contact with the bottom surface of the glass sheet; and adjusting the temperature of the mixed spent hot working fluid and newly produced hot combustion gases from the mixing chamber which is to come into contact with the top surface of the glass sheet, the adjusting of the temperature of the mixed fluids which are to come into contact with the top and bottom surfaces, respectively, of the glass sheet, being adjustable independently of each other.
 4. A process for heating a glass sheet in a forced convection heating apparatus wherein the apparatus includes a housing having an interior region and the glass sheet has a top and a bottom surface, the process comprising the steps of:producing hot combustion gases from a first gas burner; producing hot combustion gases from a second gas burner; distributing the hot combustion gases from the first gas burner toward and into operable contact with the bottom surface of the glass sheet within the interior region of the housing; distributing the hot combustion gases from the second gas burner toward and into operable contact with the top surface of the glass sheet within the interior region of the housing; controlling impingement velocity of the hot combustion gases being distributed from the first gas burner toward and onto the bottom surface of the glass sheet within the interior region of the housing; and controlling impingement velocity of the hot combustion gases being distributed from the second gas burner toward and onto the top surface of the glass sheet, the controlling of the impingement velocity of the hot combustion gases being distributed from the first and second gas burners, respectively, being controllable, independently of each other. 